How to remove background?
You can use masks to isolate your objects from the background. These masks can be animated with keyframes or attached to a tracker to stay on the objects. But it is quite cumbersome.

Masking tutorial: http://learningblender3dsoftware.blogspot.de/2012/10/blender-264-tutorial-intro-to-masking.html

Video tutorial which covers masks in combination with Trackers: http://www.blenderdiplom.com/en/tutorials/all-tutorials/424-tutorial-sin-city-effect-in-blender.html (click the third link below the video: "8:50 - 12:40 ...")

Blender wiki: http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.64/Mask_Editor